The present invention relates to an odor identifying apparatus for identifying an odor component in a sample gas provided with one or a plurality of gas sensors.
The odor identifying apparatus of this type is used for obtaining odor intensity and odor quality in research and development fields relating to odors, flavors or fragrances (hereinafter simply referred to as xe2x80x9codorxe2x80x9d) of foods and perfumes; in quality control fields relating to odors of foods and production of chemical products; and in control or management fields of an odor environment.
Heretofore, measurement of the odor has mainly been made through a component analysis using a gas chromatograph/mass spectrometry (hereinafter referred to as xe2x80x9cGC/MSxe2x80x9d). However, there have been various defects such that the component analysis using the GC/MS takes a long time; skills and experiences are required; it is difficult to analyze and interpret too much output information relating to a sample; and it is very difficult to obtain a correlation with a sensory or organoleptic value of the odor.
Thus, there has been proposed an odor identifying apparatus using a gas sensor wherein the above-described defects are solved. As a gas sensor to be used in the odor identifying apparatus, there are mentioned an oxide semiconductor sensor, electrically conductive high polymer sensor, a sensor wherein a gas absorption film is formed on a surface of a quartz oscillator, i.e. quartz crystal microbalance (hereinafter referred to xe2x80x9cQCMxe2x80x9d), and a sensor wherein a gas adsorption film is formed on a surface of a surface acoustic wave (hereinafter referred to xe2x80x9cSAWxe2x80x9d) device. In the oxide semiconductor sensor, there is used a phenomenon wherein an electric resistance of the oxide semiconductor is changed by an oxidation reduction reaction of gas components in a sample gas. In the electrically conductive high polymer sensor, there is used a phenomenon wherein a conductance of an electrically conductive high polymer is changed by adsorption of the gas components. In QCM and SAW device, there is used a phenomenon wherein a frequency is changed according to a weight change when the gas components are adsorbed by the gas adsorption film.
In the odor identifying apparatus for measuring the odor components in the sample gas by using the above-described phenomena, there is provided one or a plurality of gas sensors having different response characteristics with respect to the odor components, wherein a signal detected by the gas sensor is displayed as it is, or signals detected by the plural gas sensors are subjected to a multivariate analysis. In other words, the odor components in the sample gas are measured by applying a technique what is called chemometrics.
There is an odor identifying apparatus including a collecting portion filled with a collecting agent for absorbing odor components in a sample gas. In the odor identifying apparatus, the sample gas is introduced into the collecting portion to allow the collecting agent to absorb the odor components; a drying gas, such as a nitrogen gas, is introduced into the collecting portion to dry the circumference of the odor components; the collecting portion is heated to separate the odor components absorbed by the collecting agent; and a carrier gas is supplied to the collecting portion at a predetermined flow rate, so that the odor components are guided to the gas sensor by the carrier gas for measurement.
In the odor identifying apparatus using the gas sensor, an output for one sample gas in one measurement is one kind with respect to one gas sensor. Therefore, there is a problem such that when compared with the GC/MS, information quantity is very small.
Therefore, in view of the above problems, the present invention has been made and an object of the invention is to provide an odor identifying apparatus, wherein a quantity of output information relating to a plurality of sensors in one measurement can be increased.
Further objects and advantages of the invention will be apparent from the following description of the invention.
An odor identifying apparatus of the invention comprises one or a plurality of gas sensors, a collecting portion filled with a collecting agent for absorbing odor components in a sample gas, a sample gas introducing portion for introducing the sample gas into the collecting portion, a heating portion for heating the collecting portion to separate the odor components absorbed by the collecting agent, and a carrier gas supply portion for supplying a carrier gas to the collecting portion to supply the separated odor components to the gas sensors. The odor identifying apparatus further comprises an expelling condition control portion for changing at least a part of an expelling condition in time sequence in one cycle of the measurement when the odor components adsorbed by the collecting agent in the collecting portion are separated.
One example in changing the expelling condition in time sequence in one cycle of the measurement is a heating temperature at the heating portion in the collecting portion.
When the odor components adsorbed by the collecting agent in the collecting portion are separated by the expelling condition control portion, the heating temperature of the collecting portion is changed stepwise from a low temperature to a high temperature. Thus, outputs of the gas sensor at the respective stages of the expelling conditions can be obtained, so that a plurality of outputs for each gas sensor can be obtained in one cycle of the measurement.
Further, in the invention, one of the expelling conditions may only be performed in one measurement. Namely, one of the heating conditions, such as from 40 to 100xc2x0 C., 100 to 150xc2x0 C., 150 to 250xc2x0 C., is selected, and the odor components at the particular temperature are obtained.
Another example for changing the expelling condition in time sequence in one cycle of the measurement is a supply flow rate of the carrier gas to the collecting portion from the carrier gas supply portion.
When the odor components adsorbed by the collecting agent in the collecting portion are separated therefrom by the expelling condition control portion, the supply flow rate of the carrier gas to the collecting portion is changed stepwise from a small flow rate to a large flow rate. Thus, the outputs of each gas sensor at the respective stages of the expelling conditions can be obtained, so that a plurality of outputs for each gas sensor can be obtained in one cycle of the measurement.